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the previous owner set up the truck with dual 12V batteries connected in series. Something drained them to the point of not being able to start. Questions are: 1. can I jump start from a 12V car and should I? 2. can I charge the batteries one at a time with a12V charger?
I have a 24V charger on order but want to start the truck sooner.
these may seem like stupid questions but I'm new to 24V vehicles systems.
Usually trying to jump start a 24 volt system with your 12 volt car doesn't work because you are only hooked to one battery of the 24 volt system. Charging each battery separately with a battery charger will work fine, just takes a little longer. Just hook your charger up to each battery separately and you'll be fine.
There isn't any stupid questions here. So don't be afraid to ask:)
Yes, you can charge them one at a time.
Not sure if its necessary, but I always disconnect the short lead tying the two batteries together before charging individually.
Mine is wing nutted so that I can easily remove the jumper while I maintain the two batteries during the idle winter months.
https://i.imgur.com/gzhzOO8l.jpg
Along similar lines, I have a leaky alternator, probably a bad diode. If I were to leave the batteries connected, I would be greeted with dead batteries. So, I disconnect the link between the two 12V batteries and only connect them when I want to drive the truck. One day, I will get off of my fat (yes!) arse and replace the alternator and see if that fixes the problem.
I am not purposefully trying to sound patronizing here...but one thing I learned was to turn off the light switch on the dash. If you forget and leave it on (it's easy to do for new Mil Vehicle owners because it's a strange gizmo) the battery drains.
Or so I learnt. haha
As Don said, the most common cause of the drained batteries is a bad alternate diode. I will flatten the batteries overnight and in some cases if the battery is discharged totally will ruin the battery so it won't hold a charge.
I will disconnect the batteries when I am not using the truck to prevent the batteries from being drained.
Leaving the ignition switch on is another common problem but usually results in a dead coil instead of a dead battery.
Use military-style battery terminals they handle lots of current. and you only need a 9/16" wrench to remove the cable from the terminal. I used a wing-nut terminal on my deuce and a half because it was all I had handy at the time and it melted down.
thanks for the input, guys (or gals). I was considering putting a battery cut off switch between the batteries, the same as disconnecting. has anyone tried this?
the previous owner's set up is the same as yours, except with Optima yellow tops.Quote:
Originally Posted by jeepdan
I have done it on several of my jeeps. Use a high amp rated switch or it might melt down on you.
does a 24 volt 50 amp sound about right?
No. Hella makes a 100 amp switch. It also has a key.
http://hellahd.com/index.php/default...cs-product-11/
For convenience, $12, Amazon.
Mixed reviews...
looks good. thanks for the tipQuote:
Originally Posted by kwai
it looks like the lowest reviews seem to have a common complaint: switch failure. from the photos one reviewer posted, it appears that the switch housing was not water tight allowing corrosion. what his application was he didn't give many details to, but it would seem that extra sealing might correct the issue.Quote:
Originally Posted by ColoradoSpringsRob
also, many low reviews mention that the key fell out. I thought that was how it was designed. losing the key seems more carelessness than a manufacturer's issue.
all said and done, I think I'll give it a try. Thanks for the lead.
This is the switch I use on my CJ. It has a rough life but has never failed. Heavier duty than the Hella switch.
https://www.delcity.net/store/Master..._4877.h_169694
kinda pricey but what isn't in the M715 world.Quote:
Originally Posted by kwai
well, it turns out both batteries were dead. Battery Tender would not charge so I put a HF charger on them. One battery has recovered (I hope) so now charging the second. We shall see.
AAAARRRRGGGGHHHH!!!!
both batteries are toast. now I have to go replace them.
$$$$$$
any suggestions on what I should get?
I like the napa AGM batteries. Don't leak all over the place. Also, NAPA sells them at 30% discount on the 2nd saturday morning of the month around here. So the price is good.
Get your alternator checked. It's probably what killed the batteries.
I suspect the same. I disconnect the link between the batteries everytime I shut down the truck. No chance to drain the batteries.Quote:
Originally Posted by kwai
One day, I will have to get off of my fat arse and install the other alternator that I have. I suspect it is a good one. Arrrggghhh.
yeah, I like the NAPA AGM ones too. My son and I will be crawling all around the truck to track down the problem. The dead ones are optima yellow tops from 2017, way out of warranty. Too bad. I hear optima makes fair batteries. Not as good as they were ten years ago, I'm told, but still good.
Cue Twilight Zone music...
after I was about to give up on the optimas, I gave them one more shot with an old analog charger (circa 1973) and voila' they are fine.
hmmm...
still need to find why they went dead in the first place.
the quest continues...
I have heard that newer Optimas tend to self discharge, and experience with my own seems to bear this out. That may also be the one-wire GM alternator I have, but I have to keep the truck on a Battery Tender if I go more than a month between drives.Quote:
Originally Posted by grymsr
yeah, I have the battery tender hooked up now.I'm going to mount it eventually.
This is probably a silly suggestion, but did you leave the military light switch on? The only reason I say this is because I did that and sure enough, my battery was dead the next day. haha. Learning curve.
I didn't understand the military light switch when I first bought the truck. Unlike some of the old timers on this site, I didn't drive one of these when I was in the service.
Never heard of one myself until 1995...
I left mine on and ran the batteries down...unless the headlights or parking lights were on, it shouldnt though with good batteries...
The worse thing to do is leave the on off switch on after shutting the truck off...if the points are open, ok....if the points are closed, it will ruin the coil...
not sure what happened but I'm extra careful to switch off. but I'm probably going to install a battery cut out switch anyway.
Tenders are worth their weight in gold, Jon.Quote:
Originally Posted by brute4c
Thanks for that link Kwai, just ordered one. On a quest to figure out why my truck's electrical system hates me.
One thing I have learned of late researching RV batteries & solar charging systems is that different battery chemistries require different charging voltages. AGM requires a higher charging voltage than lead acid, and that is likely what has been at play with the Optima Blue Top (AGM) I have been running in my truck: the 12si alternator in it doesn't supply the higher voltage required by that battery, and consequently, the battery never gets fully charged.
A couple of months ago, I needed a battery charger to fill the hole between the Battery Tender and the Forney 60-amp roll-around charger/booster I have, so I bought (unintentionally) a charger with different charging programs for different chemistries. 24 hours later on the AGM setting, that Blue Top was fully charged for the first time in I don't know how long. This is when the light went on concerning charge voltage and that battery. I top it up occasionally now, and after every drive.