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5 Minutes to 15% more battery

Yahoo Message Number: 4271
How would you like to get 15% more battery power in 5 minutes? Here you go:
This all started for me when I noticed that the battery connected to the coach was loosing water faster than the battery it was connected to in parallel. That was a clue not all was well. Are the cables too long? Are the connections bad?
Here is the configuration of the batteries in Roscoe Ventura -


Primary/Secondary parallel connected batteries

For this discussion lets call the battery connected to the Coach the "primary", and the second battery that is connected by cables in parallel - the "secondary".

If all connections (Cable + Connectors) had zero resistance, or if this was AC, then it might not have been a big deal. Unfortunately this is DC. Also Cable costs money and the bigger the gauge the bigger the cost. Manufacturers know this and sometimes they save money by getting a smaller gauge than we might prefer or select for the job. Connectors also add resistance, even when they are crimped correctly. Well you get the idea.

So let's go back to my first symptom. Battery fluid was diminishing in the primary faster than the secondary. That means it was charging more, discharging more, and generally working harder. The reason has to do with DC current and is exacerbated by thin cables. But no matter how thick the cable, the distance is still greater from the coach to the Secondary battery, and this distance adds resistance, and that makes the secondary battery perform and charge more poorly. Even worse when you calculate in how much is lost from the additional connectors. So the secondary battery is delivering from between 13 to 27% less power than if resistance was zero. It can even be worse if you have a poor cable or poor connection/crimping.

Diagonal Connection: All you need to do to get out of this "degrading" condition is to hook up to the battery on the diagonals. That is illustrated in this diagram:

Diagonal connection of batteries to coach
This is such an easy change for 15% more battery capacity
AND perfectly balanced batteries. Makes you wonder why it was not hooked up this way to begin with? (Am I missing something?) Basically you are balancing the resistance and cable lengths on both batteries to balance performance.
In any case it was time for me to make the change and get the batteries balanced and working as a team. That required an easy rewire. Simply move the negative feed from the primary battery to the secondary. These are bundled in a single conduit in Roscoe Ventura, but splitting the negative feed was a simple change. (See tips below)

After - Negative coach connection on "secondary" battery

Hopefully this will stop me from my once every few months battery rotation, and it looks like it will simplify checking battery fluid levels etc.
When I started this process the batteries were reported to be fully charged, and were on a maintenance charge of 13.2V from the charge wizard. What I can tell you so far is- after making the change (See tips below) the Charge Wizard determined that the batteries were below 90%, and charged them for more than 4 hours at 14.4 volts, and then continued charging at 13.6. I will keep you posted on how this works out, or if I just end up with a pool of sulfuric acid! Hopefully all this additional charging will result in a larger pool of amps from which to pull and better battery life.
Thanks to Craig Davis for pointing me at Handybob! That and Sherlock led me to the bottom of unequal water consumption mystery! Here is a link to a more complete article
SmartGauge Electronics - Interconnecting multiple batteries to form one...
- - As usual suggestions welcome.
Kevin (Real) McCoy [KF5FUZ / WQJE447]

("Roscoe Ventura" Jayco Seneca HD SS 34 Diesel 2006; "Toad" Jeep Wrangler Unlimited 2007)

Tips:
0)Use normal precautions such as taking off your rings, use gloves, insulated tools, safety glasses, disconnect coach power, and hit the battery disconnect switch. I leave an obvious light on to show me if the situation changes while I am working.
1)Disconnect the Negative Terminal First, and then the positive terminal. Work backwards when re-connecting. That is connect Positive First and then Negative last.
2)It is always good to do one extra check on polarity when you are working on connections. Then check again!
3)If your battery has carry straps pull them back towards the back of the coach and clip them down with the battery hold down straps. This will keep them from fouling the connecting wires or the adjacent connections for the Jacks system. Use caution sliding in and out the battery tray.
4)This is a great time to clean everything and even though plastic is self lubricating; silicon lubricant on the track does not hurt. The same treatment can slow rusting on any exposed or abused metal.
5)Create room for the negative cable extension by breaking it out of the cable conduit. Then re-tape the positive bundle, and re-tape the conduit.

Negative connector separated from conduit
4) There are quite a number of positive connections. These connectors can take up a good deal of space, plus you have the jumper to the secondary battery. Space the crimp connectors out, and give them a wiggle while your are tightening the bolt so that the crimp areas do not artificially keep you from getting a good connection on all post connectors.
6) If for some reason you cannot see these photos or diagrams, please see the Roscoe Ventura album in the photos section of the group.
K

Re: 5 Minutes to 15% more battery

Reply #1 –
Yahoo Message Number: 4273
Kevin--Excellent piece!

Actually, last week, I checked out the battery setup on my new (to me) Seneca, and found the same issue with the primary battery low on water. I also noticed the somewhat unusual battery setup you described. I cleaned and re-crimped the connections to lower resistance, but tomorrow will make the change you suggest. It makes sense, especially if there is a poor connection/resistance issue.

Thanks, George (W3AML)

 

Re: 5 Minutes to 15% more battery

Reply #2 –
Yahoo Message Number: 4275

You would think this would be a "no-brainer." I just checked my golf cart... they did it right... go figure.

Denny