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Old 10-21-2010, 08:18 AM   #1
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A better battery charger

(this is gonna be long, if you have no interest in electrical projects, hit the back button now, save yourself!)

In august when I got my sunny I resurrected an old deep cycle group 24 that the PO gave me, it holds a charge and lasts for a while, but I would not bet my life it can support its advertised 75ah. I had in stock a brand new battery for a ford truck so I re-wired for 2 batteries, using these batteries until I lay into a coupel new voyagers in the spring.

since buying, we have boondocked it and run a genset for shore power about 2 hours a day, sometimes 3, and left her plugged in when back home.

all is good.

One modification we did was replace all the incandescents with leds from 'www.led4rv.com'. Let me spend a minute on this.

for $275 (ouch) I went from a total lighting load (meaning turn on every bulb inside and out) of 28.5amps to 3.3amps. I will pause a moment while you pick yourself up off the floor.

If you are a shore-power type of camper, thats ok, but if you yearn to sit way back in the woods, the LED difference is stunning. (and hey, even if you are a shore power type person what if you are also a GREEN person?)

Having been eduated as an electrical engineer the wiring circuits found in recreational vehicles I have owned/worked on appall me.

here is one reason why: battery life.

without access to shore power, a genset, or many solar panels and sunny days, boondocking with TT amenities is damn near impossible. Lets assume that there are 4 bulbs in the TT you rely on, the main room and the bedroom overheads, 2 1141's at 1.5amps (appx) each. thats 6 amps for every hour. If you have 1 75ah battery, thats a little over 12 hours of constant lighting before you get to be amish. Drop this to 4 24/28-SMD LED bulbs (at appx 200ma each) and this climbs to 93 hours.

Mind you this does not include heater blowers, vent fans, or water pumps or radios.

and we use the 75ah number loosely. sure, the brand new battery is ADVERTISED as such, but hysteresis, age, heat will shorten this, never lengthen it. at 25 amps, simple math says 3 hours. however, the real number might be closer to 2, even on a fresh battery because of heat, secondary chemical reactions etc. so a cold morning with the heater on, the stove vent on, the bathroom vent, a few lights and the water pump - reasonable expectations if you have one person showering while another cooks - will take a chunk out of the battery.

clearly, any kind of boondocking requires 2 batteries (and I know my choice of 2 mixed batteries I just happened to have is not optimal - car batteries will not take the drain and at the edge of saturation will actually draw from the deep cycle....)

so this gets me to the main thrust of my project - how to charge 2 batteries. Properly. without exploding (always a plus)

with a twist.

lets say your TT has a modern stereo in it. one with a digital clock and station memory (keep alive memory or KAM). In the 'old days' of the racous 80's and 90's, a small wire took 1 amp or less (in reality about 50ma) and powered the KAM, and a much larger fused at 10amp line was switched by the ign key and this turned the unit one.

all was well.

however, automakers noticed that in some cases, cars who switched on a lot of stuff, tended to have have ign. switch fires.

all was not well.

so radio manufacturers swapped, the amp power and KAM drew from the 10amp line and the radios used 'soft switches' keyed by ign to power up (a soft switch is nothing more than a forward biased transisitor that allows main power to flow when on. just about everything has em today)

well if you read the manual for your converter thingy, you see that the 'constant battery power lug' is to have 3 amps or less drawn from it. why is this? most, if not all of your converter charger setups charge at 3 amps max. you can verify this by either

a) RTFM
b) calculate the max current flow thru the SCR/Power tranny when the drain is fully on - the drain will be in mA and the power factor of the tranny will be 70-100 <--- this sounds too hard, I elect option 'a' above.

so, long story getting longer, we have 2 issues:

1) you are boondocking, shore power is not a reality so you must rely on a genset. boondocking by definition does not include a genset that runs for 24 hours on one tank, so lets assume you have a small gen (1400w like mine) that runs for 2hrs on one tank (like mine). How much charge can I get back in there? well, 3amps max, at 2-3 hours is 6-9ah. As I found out, it does not replace what is used overnight by the furnace. And in reality this charge is split according to internal resistance into 2 batteries. Im really only trickle charging each battery.

2) remember I said the radio was on? since it is hooked to the constant battery power lug, it is ALSO sucking on the 3 amp charger. I leave it up to the reader as a homework exercise to determine how much, but todays radios can use 10amp no sweat - actually causing a net DRAIN.

The solution: (finally)

replace the converters built in charger with a more powerful charger that is

a) turned on automatically when shore power connected
b) has a 10 amp max charge rate[1]
c) can charge 2 batteries that might be in different shape, materials, technology

This is the part where I say "hey I got a schematic in .vis, .jpg and .pdf format" but I dont know how to imbed it or upload it - pls assist?

At any rate, in your converter is a relay that isolates the batteries from the distribution panel (where all the fusey things are), connects it to the wimpy charger, and connects the distribution panel to the converter output.

cut or desolder the wire that charges the batteries. you will now be ignoring the charger output forever (or route it elsewhere to give perhaps a jack to trickle charge the tow vehicle battery.)

place a normally closed relay in between the 2 batteries on the positive side

hook one output from a 2 channel charger to each battery. (goto www.batterymart.com and look up 'NOCO RV chargers)

plug the charger into any outlet - permanently. it will draw squat (even at a crappy 90% power factor a 2 channel 10amp charger will draw about 2 amps at full load from the shore power)

Now fire the relay in (or around) the battery box via the SAME wire that fires the converter relay. (trust me on this) relays draw about 65-100ma so this wont stress anything.

the relay should be robust. since the max draw you can have from the batteries is 30a, 40 or in some cases 60amp, only half of that will come from the 2nd battery, so the normally closed contacts (n.c.) should be load capable of 30amps. any 5 pin auto motive relay will do.

How does this work? Readers digest version:

Plug into shore power and the relays fire. the batteries are positive side isolated and the coach 12v stuff runs off the converter.

so far so good.

the NOCO (or equiv) charger/tender comes online and auto senses battery type and charge level for each channel and provides up to 10amps charge rate, tapering down to trickle, and then float (like a good charger should!)

even if your radio is on, the beefier charger will power it (unless its a REALLY BIG radio) and still provide a meaningful charge.

disconnect from shore power and 3 things happen:
1) the converter relay dies, coupling coach 12v to the batteries.
2) the isolation relay dies, coupling the batteries together
3) the charger dies and its reverse flow protection (usually a simple diode) prevents it from draining even a mA.

Like I said, I have a schematic to share.

and if you read it you note I set up all grounds to be chassis grounds - both AC and DC (beleive it or not you are already wired this way in your coach)

why? you dont want any ground loops isolated cuz they will develop a potential and your trailer frame will literally corrode into nothingness. especially if it is aluminum.

Notes:

[1] - battery manufacturers recommend that the max sustained charge rate be 1% of the CCA rating. Deep Cycle batteries dont usually have a CCA rating so use a generic number like 575CCA for a 75ah. On my external smart charger I carry around, the ammeter lists 5-6amps after the first 20 minutes so they do in fact seem to be smart....
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Old 10-21-2010, 09:47 PM   #2
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Hi Quad Driver

I am into the techno stuff and have read thru your post. We have a few others on here too that may chime in. I am making some assumptions the 3 amp-charging rate you are referring to is what your existing converter is doing? Yes/No?

If so, there are newer and better options out there with a 3-stage charger to get a booddocking setup to work better.

I'm heading out camping this weekend so I'm out of time to comment a lot back to your post, but see this post and the links on it I have posted.

Battery Charger

From the digging and digging I have done, it appears that the C/8 (battery amp hour’s capacity/ 8 is the max a deep cell should be charged at repeatedly and not get cooked. You can also find folks recommending faster rates but longevity I do not know about. Using the C/8 on a 110 amp hr rated battery that is 13.75 amps charge rate. If you have 2 batteries like that, it is 27.5 amps your converter needs to supply. My Progressive Dynamics converter has it’s own algorithm that I have not yet exactly figured out yet but I can manually control the charge rate if I need to. Once the genny is up, it will quickly sense the resistance thru the battery and most all times jump right into boost mode at 14.4 volts. The current is regulated by that special algorithm.

I am too into the LED conversion; just I am easing the pain to the wallet over 3 years. Next year I will be about converted. If one is serious about boondocking, you have too almost look at this alterative that is now available. My camper is bigger and thus more bulbs at 1.3 amps each.... I have even tried the 194 bulbs that do not draw as much power but cannot see... The LED at the milli amps level is a lot better way to go.

By having my 60 amp converter, 30 amps can go to running the camper while the battery is charging leaving 30 amps available for the battery charge rate if it needs it. Mine does not get up in that range but it can if I needs it too. I have 2, grp 27 batteries. My genny/converter can take the battery back up to 90% SOC (state of charge) in about 5 hours ish or close to it. However, I am also a power miser and do daily recharges to stay ahead. I try and not ever go below 50% SOC unless something comes up that I need that extra power. Therefore, I may only be going from 60% back to 90%. Or 70% back to 90%. It will take many hours, could be almost an entire day on shore power to get that last 10% in. The system then drops to standard charge at 13.65 volts and once up at 100% goes into float mode at 13.25 volts and only milli amps of current. And the PD converter also goes into desulfation mode to properly maintian the battery.

Check out that post and I will be back Monday night to talk more.

Hope this helps

John

PS: to post your diagram, do a print screen of the what ever you are viewing it with, paste it into a picture editing software, crop out the boarders, then save as a .jpg. (640 x 480) Then upload to the site as a picture.
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Old 10-22-2010, 09:03 AM   #3
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Hi John,

I certainly understand why camping takes precedence over internet!

A lot of points in your post that I will address separate, but I want to start with (respectfully) what I feel is a misconception about RV converters/chargers.

With of course the caveat that there very well might be something NEW in the last few years that finally makes use of known technology not covered by my statements.

I refer to a posting of a file for the 'Magnetek 63xx' series converters by 'Steve Collins' a little over a year ago. IMHO this is representative of 99% of the units produced from at least the late 70's to present. link here: http://www.sunlineclub.com/forums/do...%20Centers.pdf

Fortunately, I have a link to the actual internal schematic here:
Magnetek Schematic

(suggestion: capture this as an image and save it next to Steves post. You give me an SCH for any gadgets and in most cases I can make purty good guesses on what components are used and suggest a location for repair parts...)

anyways, the sch refers to 3 main sections of the unit which I will go over. If familiar, skip over.

1) goto the upper right of the SCH and look for 'RY1' - relay one. This is the infamous isolation relay that takes the battery offline for charging. When cold (not plugged in) the N.C. contacts connect Battery RED to converter output BLUE which goes to the 12v distribution panel.

Note: the SCH does a poor job of clearly annotating when lines intersect which are joints and which are jumps. I'll point it out when it appears amibguous.

2) to the left of the relay is the AC->DC rectifying section. I had seen internet discussion where it was claimed this is half wave and therefore very dirty DC power. not true, this is full wave rectification for a center tapped transformer (T1) which apparently is a 24-30v unit and we hope of sufficient size for the stated output amperage. D1-D4 are the recifiers for each T1 output leg. Dirty power, not 'very dirty' power. This brings us to

2a) The first fix I would do is 3000uF of electrolytic caps across BLUE and WHITE at a 25v or higher rating cuz...
2b) your incandesent lights wont care. Any LED lights SHOULD not care assuming a high enuf reverse breakdown voltage, and your motors (water pump, fans) mostly wont care (but life is shorter) but your fine electronics may not like the ripple. prolly introduce a lot of noise.

3) now note the line running 'down' from the output of D3-4. I assure you it is also tied to the output of D1-2 and jumps WHITE (negative). This is the battery charger section and I will go over it roughly. Unlike an old school 'AC rectified 12v output' charger of yore, which only provides a bulk charge...

(from 10.5v up to a little over 12v, the 'state of charge' of 80-90% can be provided by almost any 11-15v source at fairly high amperage for a short time) This occurs VERY quickly overall, but if you never get into the 'absorbtion charge' phase, the battery wont last and loses overall life quickly.

SCR1 is the main output and while it APPEARS it can give the full output of the rectifier section it is limited voltage and current wise by R1. The value of R1 is not given but anyone peeking inside this thing can tell me the color banding (not likely) or the writing on a block ceramic to get the value. Suffice to say, if on shore power, the amps available are as you stated, the max value minus any used load, then limited by this - so far.

check out the operation of SCR2, D6 and D5. Long story short, any voltage at D5 will slow that charge rate. when does D5 get voltage? Well look at the only VR - the 1K they say to adjust to be 13.8-14.2 AS the battery voltage climbs the Zener (D6) will slow reverse conductance. Based on the 470/150ohm divider Im predicting its a 5.6v zener. Once it nearly stops conducting we are left with about 100mA drain current for SCR 2 which will nearly shut it off, forcing a voltage rise at D5, slowing the charger to trickle current.

I note that the manual makes the statement of 3amps at lug B, which implies the absorbtion range is at or <3amps. Any more and you risk keeping the battery at the tail end of the bulk charge zone which wont bring it up any further as the charger will 'motorboat' into bulk/absorbtion back and forth, and burn up the battery by offgassing.

All this said, with no current drains, this charger setup will taper to NEAR zero, but will never go into a true float charge and actually leave the battery alone - something will always flow so the battery will break down electrically, just over time.

Now tie this into my little project:

the first goal, via conservation etc, is to not get a battery too far into depletion. Never get below 50% for sure in the field. you need to charge almost immediately, and FULLY to save the battery longevity.

Leds and not-so-cold weather let you keep a state of charge at 80% or more.

2 75aH batteries at 80% implies 30aH came off the battery. that should be our target goal (or less) for an overnight, during the day a genset can apply power for breakfast and dinner, when 12V tasks are at a maximum.

My selection of the NOCO charger (I just so happen to own that model so I pick on it) gives me a few advantages:

1) dual channel. one thing we know you dont wanna do is apply ANY charger, high amp or trickle, to parallel batteries. if the batteries are not 100% equal it will not give the desired effect.

2) microprocessor controlled. the gizmos can not only sense the different charging methodologies needed between flooded, AGM or Gel, but can also keep a higher current for a longer time. again, if your batteries are not equal and you charge in parellel, as one battery reaches its target voltage, ther reverse flow current into the weaker battery will not be strong enuf to not force the charger into trickle mode on the magnetek.

3) long term maint. A charger has to go into true float mode to preserve a battery for long plugins. I consider my plugging in for a week between trips a long plugin.


With respect to breakers mentioned, there should be one in the charger to prevent great outflow current. This does not so much protect the battery, as it protects the wiring. (plus lets face it, 30amp charge for any more than 10 minutes cooks it.) there should ALSO be another reverse facing breaker (or fuse) from the battery for the trailer to catch when the current draw exceeds 30amps (or whatever) - this is also for wire protection. I always say if you want to efficiently light somthing on fire, light its wires on fire first via current...

I would be interested in seeing schematics from any new converters that you feel are more advanced. It would be good and long overdue I say, but I fear my latest trips to RV shows are not showing me anything new for the masses.

BTW - on the schematic I have, I have it in visio format, JPG or PDF. I WAY recommend the pdf, I tried to upload it, but it just hung forever. not sure why...I can email it
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Old 10-22-2010, 09:26 AM   #4
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Note - I found the PD 9100/9200 of which you speak. No luck on a scm just yet, but from the advertisments it does appear to be what I think RVs/boats should use vs old school.

It also says it can do multiple batteries but I have not found an n-channel provision yet
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Old 10-22-2010, 10:13 AM   #5
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Quote:
Originally Posted by quaddriver View Post
Note - I found the PD 9100/9200 of which you speak. No luck on a scm just yet, but from the advertisments it does appear to be what I think RVs/boats should use vs old school.

It also says it can do multiple batteries but I have not found an n-channel provision yet
Yep, things have changed quite a bit from the old magnatek days. There's still a large volume of single stage units produced, and those probably do wind up in the majority of new RVs. The only difference is they dropped the expensive transformer and went switchmode.

There's also a selection of microprocessor controlled, multi-mode, switchmode units out there - like the PD unit John is running. The WFCO 89XX series is another, which is what I have in my Sunline. The PD has the advantage of an "equalize" mode built-in, while the WFCO does not. Another advantage for PD is that the "intelli-power/charge wizard" models will support user manual override of the charge function (usually requires a "pendant" plugged in).

Both manufacturers have stand alone converters and power panels. John's PD is a stand alone, while the WFCO 89XX is a power panel. In the project trailer I have a Progressive Dynamics PD4000 which is a power panel with a built-in 45A converter. There's some other brands out there, like IOTA and Xantrex (or whatever they're called this week), but I am not familiar with their stuff at all.

Schematics? Seem to be state secrets. None in the manuals I have and not much found online, short of people asking for them. Both my WFCO 89XX and the PD4000 seem to work as advertised. You can clearly see the state changes with a voltmeter and ammeter. The WFCO has been floating a bank of GC2's for over 2 years now with very little water loss. I'll be able to speak more on the PD4000 once the project is done and the thing is usable.

Last year I made the jump from a pair of GC2s to 4, in series-parallel (thread here: More (battery) Power). Although I agree that running them in parallel has risks, for me I feel the benefits outweigh the risks. Keeping tabs on the bank occasionally with a quality hydrometer has shown everything in check, despite the 9 month ago difference between the sets. I did cycle the new pair a few times and brought all up to 100% SOC before joining the older set.

Cool thread, needs pics though! Would like to see some pics of that charger you are working with.

- Frank
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Old 10-23-2010, 07:04 PM   #6
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Quote:
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1) dual channel. one thing we know you dont wanna do is apply ANY charger, high amp or trickle, to parallel batteries. if the batteries are not 100% equal it will not give the desired effect.
Hey quaddriver....

I found your post VERY interesting!

I do have a question for you though. I just got done, installing a Progressive Dynamics PDM9260 converter in our fifth wheel and would like to upgrade the single group 27 coach battery to a pair of AGM batteries. Since the standard deep cycle battery needs to be vented, I am limited to only being able to have a single battery. The AGM batteries do not need to be vented, since they don't produce hydrogen gas like deep cycle batteries do.

Since I want to buy both AGM batteries at the same time, they should be very similar in construction and performance. I have never heard anything contradicting the use of batteries in parallel, until reading your post. Does it hold true for AGM's?


Gary


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Old 10-24-2010, 08:52 AM   #7
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I myself have never used AGM batteries - due to cost. IT seems I never have enuf left over on a project.

But any battery type - here is the issue I have with charging parallel: the 'machines' can measure 2 things about a battery, internal resistance, and voltage (but they can infer either if they know current flow)

when you put 2 batteries in parallel, you reduce overall resistance via:

(R1R2)/(R1+R2)

I dont see how this does not signal to a smart charger that we are approaching the top of the charge - and I fear it turns off early. On a flooded battery, if you dont finish the absorbtion phase when started, you seriously shorten life...

smart charger manus, aint talking.
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Old 10-24-2010, 03:03 PM   #8
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Originally Posted by quaddriver View Post
This is the part where I say "hey I got a schematic in .vis, .jpg and .pdf format" but I dont know how to imbed it or upload it - pls assist?
I'd love to see it!

Try this:

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Old 10-25-2010, 09:28 AM   #9
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I will try that after work....
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Old 10-25-2010, 09:29 PM   #10
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Hi Quaddriver

I’m back from camping and trying to re-read your post.

The link to Steves manual. Here this will fire off on the forum. Sunline Coach Owner's Club - Sunline Owner's Files - Magnetek Series 6300 Manual

For reasons I do not know…. We cannot direct link to a Sunline posted PDF from our manual section. It comes up an error to other users when fired. However you can link to the section is it stored in, hit “download” and then open and save it etc.

I have had some TTL logic experience from long ago. Early Late 70’s and early 80’s it was the in thing then until everything went programmable and no one wanted to deal with hard wired TTL in industrial controls...

The older controller you pointed us to, that is an older setup. Including the relay to switch from battery to internal power. I know in at least 2003 vintage the converters in use in my Sunline went right on the DC power bus. No relay and the unit could run the camper on 12VDC with no battery. Some where in ~ 2006 ish time frame newer 3 stage chargers became more popular and where showing up in the Sunlines. My 2003 unit was still older technology but it at least had 2 charge modes. 13.65 volts and 13.25 volts. No 14 and above.

See here on the one I took out. This may have been the next wave in power converter technology from the older Magnateks. This was a Centerion unit from 2003.

To your comments on using 2 batteries in parallel on a camper. H’mm this is common place now a days and can be found in many places to just hook up 2 or more batteries in parallel. However…. there is always a but…. I do agree the standard way they just show them hooking up in parallel can yield the 1st battery being used the most, changed the most and at slightly different voltages to the one next to it from a SOC charge perspective. I found this out myself this summer. I had them hooked up in parallel like many of the recommendations say to and low and behold a voltage check with the leads unhooked shows both batteries slightly different SOC.

Then I hooked them up this way. Scroll down to method 2 SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

I had them on method 1 and when I went to method 2, (I only have 2 batteries) it did force a more equal charge and more equal draw. The next time I checked after connecting this way, both batteries where at the same voltage when I unhooked the leads to check.

Method 1 truly draws on the 1st battery and recharges the 1st battery 1st and the rest spills over to the 2nd battery. So by going to method 2 I feel I have made it the best I can with what I have to work with.

Your point is valid about how can the charger knows which battery is lower, but it may also be a small enough amount that the average camper person has no idea one battery is actually at 97% when the other is 99 or 100% and they equalize out to what they feel is OK. I would of never found it myself if I had not unhooked the parallel leads and check each battery independently.

If you want to do your system the way you are describing, cool. It can make it the best you have to start with. But the newer ones do put out more then 3 amps and have more actual working features.

There is one thing I have found in my battery education process from RV’ing is about desulfation of the battery. That is a key component to getting the most from your batteries. My new PD has it built in so I gain that benefit when I’m out camping but I also use a stand alone Battery Minder Plus when the camper is home, I plug this into it. In my case it is easier then running a monster long cord to the PD. I have a rotary disconnect switch on the batteries lead and plug this in. BatteryMINDer® Plus 12 Volt 1.33 Amp Charger-Maintainer-Conditioner (Desulfator) | All | Battery Chargers by BatteryMINDers.com

Also since learning of desulfation I have them on my tractors and lawn mower. I can tell they help especially on the wimpy lawn mower batteries. I gained so far 3 years more out of the one in my riding lawn mower as I could only ever get 2 to 3 years out of them and now I’m on 5 and counting.

I do not have a schematic on my new PD converter but I do have a on line volt meter so I keep tack of it’s charging modes. You can see here is in normal charge mode now.


The other thing that is good is I only top off the battery water once a season so what ever I’m doing is working. I check it and it really does not move much at all even going thru the charge cycles.

I fully agree with your 50% recharge point and then bring it back up soon. I have read that in many places and with keeping up to 100% and desulfated while not camping so far has worked out well.

I now have a clamp on DC amp probe so I can get a better handle on the charge rates next time I go boondocking. Frank has a shunt unit permanently mounted and I may get there too after I get some of the other “to do” things done.

Good tech talk and good luck with your upgrade.

John
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Old 10-26-2010, 04:16 AM   #11
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SUN #1508
quaddriver is an unknown quantity at this point
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btw that battery minder? its exactly the same model I have in the shed to keep up on the tractor and atvs.
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QuadDriver
1987 2461 behind a 1981 F100 and sometimes my 1990 F150
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