Golf Cart batts re-positioning & wiring diagrams

[Stephen Butler]

We have the 4 golf cart batteries, wired per Mainesail's diagram.  A related question that we have asked  before, but have not received an answer, or at least one I can remember.   Other than acting as a backup, is a starting battery needed for our engine size?  We do have a Honda 1000 for emergency charging.  Thanks for any insights!

[Stu Jackson]

Steve, no.  It IS just as a backup in case your house bank dies for any reason: overuse overnight, catastrophic failure, that sort of thing.  Both Maine Sail and I use the house bank to start the engine all the time, regularly check the reserve bank (by voltage and using it occasionally) and have had success for over 15 years with this setup.

[mainesail]

We have the 4 golf cart batteries, wired per Mainesail's diagram.  A related question that we have asked  before, but have not received an answer, or at least one I can remember.   Other than acting as a backup, is a starting battery needed for our engine size?  We do have a Honda 1000 for emergency charging.  Thanks for any insights!

No you don't have to, it is a personal choice. For the cost of a "reserve" bank it is never a bad idea.

Just yesterday I was working on a J-42 that currently has no emergency bank, just a house bank.

I was there trouble shooting his failed Link 2000R. The "R" means it was also his alternator regulator. He lives on a mooring.

Had he not been the attentive owner that he is he could have easily killed the house bank and not noticed. As it was the expensive Lifelines were at 11.2V when I got there....

There are MANY boats out there without adequate safe guards such as battery monitors or additional volt meters in addition to a battery monitor. Lucky for this owner his J-Boat has multiple voltage displays in addition to the Link 2000R that completely failed. he was able to notice that the voltage was steadily dropping and modified his use accordingly.

Had he only had the Link 2000R he may have "assumed" the display just went dead and eventually been left dead in the water because he also had no alternator... In his case everything the Link 2000R controlled was inoperable from the inverter/charger to the alternator regulator to the battery monitor..

I will be installing a "reserve bank" for him, as well as new regulator, battery monitor and I/C remote & a small solar array in the next three weeks.... He learned his lesson and now wants a suitably big reserve bank of two group 31's....

[Stephen Butler]

Thank you Stu and MaineSail.  Much appreciate the response.

[Roc]

I re-positioned the wires so they now balance the batteries like Mainesail suggests.  I added a neg. buss bar and ran one neg. wire to the opposite side as the picture suggests.  The question I have is does it really matter which neg. post the battery temp sensor is mounted?  On one neg. post, I have the large wire leading to the buss bar, along with the jumper wire.  On the other neg. post, I have only the other end of the jumper wire.  There is no room to put the temp sensor on the wire which has the two wires connected, so I can only fit it on the neg. post that has the one jumper wire.  Should the temp sensor be mounted on the post that "balances" the batt bank (shown as GND Yes)?  Or can it be on the other post (where Mainesail marked as GRN No)?  Interested in any thoughts on this...


I posted this question the other day.  Any thoughts about it making any difference which post the battery temp. sensor is mounted?  Read original post above.

Thanks
Roc-

[Bobg]

my house bank is wired as mainsail suggests, I have a Alternator charging wire connected direct to the house bank, it is on the same terminal as the positive wire to the electrical panel.  Is that where it should be?  My bilge switch is also connected there, as is the positive connection to my vitron battery monitor Thank you

[Stu Jackson]

Bob, yes, you're right.

[mainesail]

Place it on which ever battery has more potential for getting the warmest... If one is closer to a water heater or engine or sunny side of the boat at a dock then put it on that battery..

[Roc]

Thanks Mainesail, I appreciate your advice.

[KWKloeber]

This is how to wire parallel batteries to help keep them balanced.


This is exactly how NOT to wire parallel batteries..

It's an OLD post, but a current (ugh! ) question, so I tacked onto the same thread.

Rod (or J? anyone?) -- I believe your assertion that method 1 is best, but....  WHY? I mean how (phenomenon?) does B1 become unbalanced compared to B4, unless there is serious V loss across the cables and/or terminal connections (improper size or installation)? 

I in each (B1, B2, B3, B4) should depend on the resistance, ass/u/ming that V is ~the same at each circuit node (very low resistance in cables and terminals.)  From experience, how much could the B1 > B4 imbalance amount to? 10%, 20%
If V loss is the cause, would it be "best" to charge something like this?:

[mainesail]

There are multiple methods that create better balance in a parallel wired system than the end connection scheme we see all to often. The bottom one you show is excellent, better than the one I and most battery manufacturers show, but if I had a dime for every-time I saw it messed up in execution, well...

The other better balance method would be the star config where each battery has an equal length cable going to a pos & neg bus. The problem here is having the exact same resistance in each cable. The drawing I show is a big improvement over an end connection, and more importantly very simple to execute, but you can do better, if it is done correctly.

For series 6V batteries there is also the "box" wiring scheme but you also don't see me recommending that one much either as I see it screwed up and misunderstood far too often as well.



But what would EnerSys know about batteries......

Quote = Odyssey/Enersys:

"Parallel Connections:
It is common to have batteries connected in parallel to
achieve a desired amp-hour capacity. This is done by
connecting all the positives to each other and all the
negatives to each other.

Typically the positive and negative leads to the load
are taken from the same battery; usually the leads from
the first battery are used. This is not a good practice.
Instead, a better technique to connect the load is to take
the positive lead from one end of the pack (the first or last
battery) and the negative lead from the other end of the pack.

The two methods are illustrated above. Solid lines and
arrows indicate positive terminals and leads; broken lines
and arrows indicate negative terminals and leads.

In both illustrations, the positive leads are connected to
each other; similarly the negative leads are connected to
each other. The only difference is that in the first illustration
the positive and negative leads to the load come from the
first and last batteries. In the second case, both leads to
the load are tapped from the same battery.

The first schematic is recommended whenever batteries
are hooked up in parallel to increase battery capacity.
With this wiring, all batteries are forced to share both charge
and discharge currents. In contrast, a closer inspection
of the second schematic shows that it is possible for only
the battery whose terminals are tapped to support the load.
Implementing the first schematic eliminates this possibility
and is therefore a better one."

End Quote

[KWKloeber]

Thanks Rod!

That blurb from Enersys is another yule log on the fire supporting the correct hookup.

So differing resistances (cables, terminals, batteries) is the bane of equal charging -- but it begs 3 question --

1. As B1 fully charges, resistance drops it out (then B2, and so on)-- so why don't all (eventually) charge as well?  Is it as simple as the engine typically doesn't charge long enough for the V across all posts to fully equalize, or is there something else going on?   (I'm talking OEM/Moto 55 amp/wet cells here, not suped-up charging/ACR/AGM/etc.)

2. Mixing battery age, types, capacity in a bank is verboten.  So why is it Ok to charge the house and a "start/reserve" using BOTH on the selector switch?  It's just one big parallel bank with one of unmatched type, age, and capacity (and probably different V loss on the cables.)

3. If the cables were infinitely large/terminals no resistance (frictionless pulley), unbalanced charging would not occur?

-k

[mainesail]

Thanks Rod!

That blurb from Enersys is another yule log on the fire supporting the correct hookup.

So differing resistances (cables, terminals, batteries) is the bane of equal charging -- but it begs 3 question --

1. As B1 fully charges, resistance drops it out (then B2, and so on)-- so why don't all (eventually) charge as well?  Is it as simple as the engine typically doesn't charge long enough for the V across all posts to fully equalize, or is there something else going on?   (I'm talking OEM/Moto 55 amp/wet cells here, not suped-up charging/ACR/AGM/etc.)

2. Mixing battery age, types, capacity in a bank is verboten.  So why is it Ok to charge the house and a "start/reserve" using BOTH on the selector switch?  It's just one big parallel bank with one of unmatched type, age, and capacity (and probably different V loss on the cables.)

3. If the cables were infinitely large/terminals no resistance (frictionless pulley), unbalanced charging would not occur?

-k

It all comes down to slight variances in voltage, under load or charge, meaning one battery works less hard (the one furthest away) or one works harder than the others (the one with the connections). I know Chris Gibson of Smartgauge did a whole write up on it but I don't recall where that is. All I need to know is that wiring for balanced banks works better than not wiring for balance. I know this from countless Ah capacity tests of banks wired using correct and incorrect methods. After a couple of years the differences are certainly measurable and consistently repeat themselves over and over.

It's not just EnerSys who show opposite end wiring of a parallel bank, it's pretty much every battery maker I know of...

[KWKloeber]

  thank you Rod. I'll search 'round for that write up.

Ken

[KWKloeber]

Rod maybe this is the writeup? I att'd a copy for anyone's use and will put it in the techwiki.

[ed]
http://c34.org/wiki/index.php?title=Electrical#Batteries