question

straycat avatar image
straycat asked

How to wire two DC/DC chargers with two engines to a single battery bank?

Hi,

We have a sailing catamaran fitted with two diesle engines and a single LiFePO4 battery bank. I have fitted two DC/DC (30A) chargers to each engine. They both work fine when running individually, however when both alternators (engines) are runing, the chanrging amps do not increase. The amps are simple the same as a single engine/alternator. Any ideas?

orion dc-dc
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4 Answers
mvas avatar image
mvas answered ·

So, what happens when both are connected? Exactly how many amps flows with one charger connected vs when both chargers are connected? Is there a 50%-50% split or is one ON full and the other is OFF? Are you in bulk mode charging? What is the config in each, to detect Engine ON and Engine Shutdown? What is the voltage at each INPUT vs the voltage of the LiFePO4 battery bank? Do you have any common / shared wires?

2 comments
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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·
And what does the VictronConnect app show?
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straycat avatar image straycat Matthias Lange - DE ♦ commented ·

both charge at about 30 amp. When running together I get about the same amps. The app shows both in bulk mode.

The Cerbo shows similar charging power both or with only each running

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Kevin Windrem avatar image
Kevin Windrem answered ·

Also, make sure the chargers are in fact in charge mode, not power supply mode.

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straycat avatar image straycat commented ·
Yip. Both in charge mode
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Michelle Konzack avatar image
Michelle Konzack answered ·

What about cable dimension and BOTH lengths from the ALTERNATORS to the DC/DC Charger and then from the DC/DC Charger to the Battery?


It seems, you have too small diameter (I would not recommend under 10mm² and the cables between the DC/DC chargers and the Battery are different lenght.


Hence the one with the shorter cable would charge at hell with 30A, but the second has switched off because of the voltage drop on the longer cable

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straycat avatar image
straycat answered ·

Cable lengths are similar but not exact. I have used 8mm2.

So if I go to 10mm2 (from starter batt and to LiFePO4), will the cable lengths not matter?

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