the right charger for 4 batterys

[vtboater]

hello, i have a 1988 30ft larson cruiser, with4 interstate12 volt dual purpose batteries,group 29,cca675,mca845,rc(min)210, what would be a decent charger, boat sets in marine on shore power from sunday night to friday evening ,we ancor out on friday + saturday night then we h ead back to marina sunday afternoon ,my 15 amp 2 bank charger is not doing the job ! we do not have nor want a inverter,we have a new 2.7 cu refer,vacum toilet, new water pump, we sometimes run our 19" ac/dc skyworth tv, all in all very simple boat on the electrical side, boat came with 2 batterys and i added to 2 more, should i have added just i more?? will appreciate all advice

 

[Greg Mrozinski]

Re: the right charger for 4 batterys

VT,

If you have four batteries you will need a four bank charger or dual two bank chargers. Trying to charge two sets of two batteries in parallel will not work. Two batteries connected in paralell on a charging circuit "fools" the voltage regulator into thinking the battery is charged (combined voltage)when in fact the two are not. This is true with your alternator as well. If your battery selector is in the "Both" position your alternators will not charge both batteries at the same time, at least not very well or properly. You need to isolate the batteries individually for charging purposes. You could use the existing charger but you have to switch the bateries to charge two at a time one on each bank and then rotate them out for the other two.

 

[Silvertip]

Re: the right charger for 4 batterys

That is utter nonsense! A tractor/trailer rig has up to six large batteries all in parallel and the engine voltage regulator is NOT FOOLED. Voltage regulators are not battery sensitive. They monitor SYSTEM voltage. The larger or most deeply discharged battery in a parallel system will hold down system voltage until the voltage regulator cutoff voltage is reached at which time both batteries will measure the same voltage.

As for your four battery system, you have more than a "simple" electrical system so current draw is an issue. You have a relatively simple solution however. An additional two bank charger (10 - 15 amp outputs) can be added along with the one you have now. If you have two separate banks (two batteries each), install the existing two bank on one bank and new one on the other bank. The larger capacity of the two chargers should go on the bank with the highest current draw. If all four batteries are in parallel forming one big system, then the two chargers can be bridged (paralleled). The combined power should keep them topped off.

 

[Greg Mrozinski]

Re: the right charger for 4 batterys

Wow, nonsense huh.

A tractor trailer with that many batteries in parallel has a charging system speciifcally designed for that application. A simple charging system on a boat designed for maybe two batteries that has had two additonal batteries added to it is not.
Maybe my choice of words could have been better but I was trying to keep it simple. Two batteries in parallel connected to one bank of most chargers will not charge properly. Simple voltage regulators are not sensitive enough to allow a full charge. This is especially true with OEM alternators.

Strange how my suggestion was the same as yours...add another charger. I guess my degree in mineral engineering and chemical metallurgy and my 29 years experience as a mechanical engineer has failed me again. Sorry, VT.

 

[Silvertip]

Re: the right charger for 4 batterys

So you are suggesting that a tractor trailer rig has six regulators? Funny how that might work since all six regulators would still montor the SYSTEM since the batteries are wired in PARALLEL and hence they could not differentiate which battery they were attached to. Yes - the tractor has a huge alternator but that is of no consequence. A 10 amp single bank charger can charge six big batteries. It is a matter of how long you must wait until that six battery bank is fully charged and what the electrical demand is. The only requirement is that the alternator must be capable of keeping up with demand. A dual, triple, quad, hex, octo or any any other combination of batteries in parallel still appears as one giant battery to a charging system. It has no idea, nor does it care how many batteries make up that system.

I was on the scene Monday morning where a dead semi had a lane of traffic blocked due to dead batteries. Another rig had tried to pull start the rig but with no air pressure the brakes were locked. With no other alternative, the second rig was pulled along side the first and a pair of jumper cables were strung between the two. You now have 12 very large batteries in parallel. Since attempting to start the dead rig immediately would fry the cables, the operational rig was left running for about half an hour to get a fair amount of juice into the second rig. The voltmeter on the charging rig was pulled off it's normal setting for about 10 minutes before the two systems began to equalize. The dead rig started fine. The lesson here is that charging systems are not magic. One alternator, one regulator, and as many batteries as you want to hang on it. It is all about alternator capacity and total load it must maintain. Not the fact that the batteries are in parallel.

 

[Greg Mrozinski]

Re: the right charger for 4 batterys

I never suggested anything of the sort. I never mentioned anything about multiple regulators. I never mentioned anything about tractor trailer charging systems.

I thought the purpose of this forum was to help answer specific questions about boats, not run on about how you know about a certain topic. I am sure you know a lot about tractor trailers and such. Great. I am happy for you.

Hey VT! If you are still listening and haven't been turned off by Silvertip's diatribe, try calling the technical folks from the manufacture of your current charger and ask them about your situation. I am sure they will be happy to discuss your problem and recommend an easy solution. Good luck.

 

[seabob4]

Re: the right charger for 4 batterys

Either get a 2nd 2-bank charger or go with a new 4-bank. If you get a 2nd 2-bank, simply wire it to the same breaker on your AC panel so they both come on when you turn on your charger.

 

[Silvertip]

Re: the right charger for 4 batterys

Here is your response to the original question: Trying to charge two sets of two batteries in parallel will not work. Two batteries connected in paralell on a charging circuit "fools" the voltage regulator into thinking the battery is charged (combined voltage)when in fact the two are not. This is true with your alternator as well. If your battery selector is in the "Both" position your alternators will not charge both batteries at the same time, at least not very well or properly. You need to isolate the batteries individually for charging purposes. You could use the existing charger but you have to switch the bateries to charge two at a time one on each bank and then rotate them out for the other two.

There isn't one true statement in that response.

So please explain why you feel the charging system on a truck, car, semi, or any other alternator system is different than on a boat. This is about batteries, charging them, and whether it is acceptable to charge them in parallel. The semi was an example. The dual battery switches that are constantly discussed on this forum are made with a BOTH setting for the very purpose of charging parallel batteries. And larger boats can have a heck of a lot larger battery bank than two batteries and they indeed are connected in parallel. Do you really think they would build dual battery switches if they didn't work? You might also be interested to know that battery manufacturers charge very large banks of batteries -- all connected in parallel. So please explain why you told the poster this should not be done. I can also point you to the charging system on any of the GM diesel powered cars of the late 70's and 80's. They had dual batteries without a switch and other than that this was a standard charging system. No different than you would find in an I/O today. Prove to us that this is a bad idea as you suggest it is.

 

[q5ka]

Re: the right charger for 4 batterys

You can have as many batteries in parallel as you want and not worry about much. Any charging device you have hooked up will charge the batteries. It will just take twice as long now. Same as your alternator, it will take longer. Think of it like a garden hose with a 4 way valve at the end. You only have 1 open (one battery) all the power goes to that one outlet. Two open and same amount but split between two outles so each get half as much if only 1 open. Now all 4 are open, 1/4 the pressure (amps in current terms) to each as compared to only 1 being opened. So you have a 4 amp battery charger, each will really be getting about 1 amp of charge.

The only reason you would need more than 1 bank for charging is if you have more than 1 circuit. Example, 1 bank for the started and 1 bank for house (which is what I have). So I have a battery that runs just the starter. This way if I was sitting too long with the radio on, I can still start the boat. You could also have with your 4 batteries, 1 starter, 1 fridge, 2 for rest of house. That would require 3 circuits going to their respecive locations, 3 different charging banks, and an isolator from the alternator so the motor can maintain all 3 banks.

The idea of it not working is wrong. My Dodge diesel truck would not work then with its two batteries in parallel. Most 24v semi (tractor) trucks would not work. Electric golf carts would be bad. Your rechargable batteries in your remote control would also not work. Just look around to the many items that work in this configuration. It is a solid and tested configuration.

One item to note, if one battery gets weak, the whole systems tends to suffer so battery maintance is as important as ever. Also there has been some talk about using 6v batteries instead of 12v. 6v often has more amp hours which means longer run time.

 

[vtboater]

Re: the right charger for 4 batterys

thanks for all the feedbacks ,looking at noco+ min kota 4 bank chargers don,t know the one i,ll pick yet,have not found a guest4 banker yet, any suggestions?? thanks!!

 

[Silvertip]

Re: the right charger for 4 batterys

I still feel you are better off with two, two-bank units. Replacing a four bank charger is a heck of a price to pay if one bank goes down.

 

[Greg Mrozinski]

Re: the right charger for 4 batterys

I totally agree with all of the suggestions. If you read my original post I basically said the same thing...maybe I should have used a few different words to make my point. I wasn?t trying to say that you couldn't charge batteries in parallel but rather with the charger specified by the original poster (10 amp) it "wouldn't work" meaning the batteries may never get fully charged because the source was possibly too small or the charger as configured wasn't up to the task, etc. My point about regulation of the charge (with this charger) goes along with q5?s comment about battery condition and applying enough or possibly too little total charge. Most marine chargers are designed for one battery per charging bank.

I am surprised no one chimed in about different battery types and the significance of charging profile with respect to wet cell vs. AGM and Gel cell. One can spend a lot of money on a battery and get half the life out of it because of improper set-up of the charging system.