Xantrex chargers

J

Jimbo

New member
I am adding a second house battery that is exactly the same as my original.
I currently have a Xantrex charger Model TC10TB which is now charging my house battery and starting battery.
Can I add the second house battery (just parallel to first) and keep the current charger or do I have to go for the 3 battery unit?
I can live with the recovery time being slower, only use it when at home, just to keep them topped up.
Jimbo
 
Jimbo-

If both your house batteries are in top condition and otherwise equal, you should be able to let one of your two charging circuits just charge the two house batteries in parallel, with the other one working on charging your starting battery.

Just be sure to disconnect the parallel switch when finished charging (you'll have automatically switched to trickle charge at that point).

We hear a lot of warnings about batteries connected in parallel circuits, but as long as they're kept in equal condition, routinely charged, and paralleled only while in use or being charged, I've never had any problem with doing so, even when using up to 4 batteries in parallel.

To be sure, there are a lot of good warnings about the dangers of two dissimilar batteries or batteries of different condition causing problems when connected in parallel during the charging, discharge, and resting states, but keeping them very equal seems to be the key, including-

1. checking their charge state (voltage) after a rest period following a charging session to see that they're really equal, and

2. discharging them in parallel so the voltage drop in the batteries is equal and they will be equally ready to take a charge, not at different voltage states where the strong one discharges into the weaker one and the weaker one absorbs the greater charge rate, etc.

Some of this may not go down perfectly with the conventional battery wisdom we usually hear, but seems to work for me with my experience with marine applications.

Part of the success may lie in very vigilant monitoring of battery states and keeping the batteries in a very constant state of full charge. I don't run batteries down hard every unless of an accidental oversight.

Hope this helps!

Joe. :teeth :thup
 
Xantrex charger Model TC10TB has two output terminals. You should not have to parallel the batteries--if this is correct. Just hook up a second positive wire to the new battery.

By defination the new battery will not be equal to the old battery because the old one has been used, and will have slightly less capacity.

Theoretically batteries should be equal, BUT, we have crossed several oceans with somewhat discimilar battery banks--and by careful monitering there was not problem. This required charging at 150 to 300 amps (two source of charging--a 150 amp alternator and a 130 amp output from an inverter.) In the real world it is not practical or even possiable to replace all batteries with exactly the same batteries.
 
OK, here's a third opinion. First, I take it that you already have two batteries on your boat's charger. Adding a third means that you want to parallel 2 ea. batteries on one output. Now for the third opinion.

Two parallel batteries offer several problems, AFTER they're charged. When they're being charged each battery will get a certain portion of the charging current, depending on all those factors Joe mentioned above. When you're down to a trickle charge or less, one battery will feed the other unless they're exactly the same. To get them close enough, you'd have to buy two new batteries. Or you could separate the batteries AFTER the charge. To separate them, you could put diodes or a switch in each charge line. The diodes do it automatically, the switch manually.

I realize that you have the 10TB, and the next step up is $250. However that family of Xantrex charger also shuts down and comes back on to top off the batteries, etc which makes it hard to predict what is going to happen. So try it and see what happens, using Joe's advice. Personally, since we depend on our batteries when we cruise, I'd have the batteries separate and I do have the three output Xantrex 40+, using only 2 out of the 3. What the heck.

Boris
 
My appologies, I missed that there was a starting battery and house battery--thus two batteries already. Never the less, you can still get by with paralleling the two house batteries of different ages. What is the "risk"--boiling off electrolyte? Since the batteries are the same size and only different ages, there will be some difference, but as long as you watch the water, I doubt that there will be any problem, since the TC10TB is a 3 stage charger, when it goes into float charge, the difference in battery voltage will be minimal, and it will not be in a mode where there is a risk of boiling off electrolyte.

In reality when you have two batteries which are always in parallel, they are always at the same voltage (maybe you loose a slightly amount of capacity of the newer battery)--but there is no danger. It is not as if you have one battery at 13.8 volts and another battery which is at 11 volts, and high current flows when you connect them---that is a much different situation.

There was a long thread on THT about mixing batteries--and this can be done for charging also--as long as the voltages are compatable and charging characteristics are similar.

The Xantrex TC 10 TB is similar to the TC 20 and 40 chargers and in the float stage has a very low current flow, if any.

This is a chance to do an experiment. Put the old battery on the charger for 3 days, and then the new battery on the charger for 3 days. Take the battery off the charger and measure the voltage (to .01 places).. at 12 hours after you disconnect the charge. Compare the two batteries. My suspecian is that you will only see a few hundredths of a volt difference. If this is the case, it would be interesting to see how much current flows from one battery to the other--There might be a small amount initially, but after they have been connected for several hours, taken apart, and then reconnected.
 
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