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Adam Robb avatar image
Adam Robb asked

Why is it okay to have Lithium bank and Starter battery combined with Cyrix Li-CT

Hi, I would like some further information on why its okay to use a Cyrix Li-CT to combine your Starter battery to your Lithium batteries?

-Wouldn't there be a possible chance that you can overcharge your start battery as the Lithium will be just continually taking as much amps as possible?

-When charging via solar or shore power you will also have your batteries combined.
-I wouldn't think that have a Gel or Lead acid battery connected into your Lithium system would be a great idea

Wouldn't putting a 3 stage regulator (so the alternator doesn't burn out) on your alternator to charge your lithium and then a DC-DC charger to your starts be the safest option?

Looking for the best and safest way to utilize the alternator in lithium installs.

Cheers

Cyrix Battery Combiner
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2 Answers
Paul B avatar image
Paul B answered ·

A lead acid battery full its sitting voltage is around 12.7 v

a Lithium Phosphate is around 13.2

so if there was no relay then the Lifep04 would slowly discharge into the LA battery until the voltages were equal. Always highest to lowest is the flow

when charging they are both around 14.4 from the charging source or the alternator is above there sitting voltage's, again highest voltage the current then flows to the lowest voltage.

so the Cyrix will close when is above its set value and thus lithium voltage then the alternator or the other charge source will feed both batteries as needed, no power is drained from the lithium/Lifep04 or the LA this way.


hope the above helps


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Adam Robb avatar image Adam Robb commented ·

Im not really following you. Wont you still be getting a high amount of amps going towards the LA when the alternator is running as the Lithium would be asking for it? And also having a mixed bank of LA and Lithium for certain amounts of time isn't really healthy for the batteries is it?

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Justin Cook avatar image
Justin Cook answered ·

Hi @Adam Robb, welcome to the Community!

A Cyrix-li-ct can be used as you describe, but the best and safest solution for charging your LFP bank from your alternator (through the start battery) is a DC-DC charger, as it not only provides current limiting to protect your alternator, but also provides an intelligent charge profile to protect your LFP bank.

The Cyrix-li product range is appropriate for a number of very particular installation conditions, but should certainly never be mistaken for a viable alternative to a good DC-DC charger like the Orion-Tr Smart.

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Adam Robb avatar image Adam Robb commented ·

Hey mate,
Agreed! A DC-DC charger is the way to go. It’s just been baffling me why in a lot of forums and diagrams from Victron they have been using the Cyrix-Li Ct as a way to charge your lithium from your alternators. However instead of charging your start bank I prefer to install a external 3-stage regulator that is programmable for lithium characteristics (wakespeed ws500 is a great one) then using the Orion to charge the Start batteries. That way your really get the most out of your alternators when you have larger banks (1200ah) with larger alternators (120amp).

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