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dannen avatar image
dannen asked

Cyrix-ct 120 - Different battery types

Hi,


I just bought a Cyrix-ct 120. My startbattery is a couple of years old sealed lead acid battery and my house battery is a brand new AGM battery.

My alternator is connected to my start battery.

I also have a solar panel and an MPPT 100/20 regulator which is connect to my house battery.


Is it OK to have different battery types connected to the Cyrix, or will I damage my batteries. For Example the SmartSolar MPPT is det for AGM charging, hyras This voile potentiellt over charge my startbattery since Cyrix is bi-directional?


Also do I risk that my older startbattery will wear down my new AGM battery the the breaker is closed due to solarcharge or the alternator?




Cyrix Battery Combiner
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4 Answers
dannen avatar image
dannen answered ·

Or my best option to sell the Cyrix-ct and buy a Renogy DC-DC Charger for example?

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Justin Cook avatar image Justin Cook ♦♦ commented ·

I like the B2B option better in this case for sure; realistically the Cyrix should be fine but I've found them to be fairly finicky in certain situations, and a B2B would definitely allow you a much greater level of control over your charging conditions (although @Wildebus suggestion to just hook up a ground disconnect switch to the Cyrix is a perfectly viable one and one that I've done myself).

That being said, I generally try to steer people away from Renogy products; not because they're necessarily bad products, but because they're not necessarily good products either, since Renogy is a re-branding company rather than an actual manufacturer, which to me translates to questionable products with questionable warranties.

I'd personally and professionally recommend a Sterling B2B if you're going the B2B route; yes, Sterling is more expensive than Renogy, but a Sterling B2B is actually manufactured by Sterling, and fully warranted and supported by Sterling and its distributors. On a personal level, when dealing with systems I'm relying on, I'd rather pay a bit more to have the reliability and support of a known company and established product... just my two cents.

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David avatar image
David answered ·

An option can be to get a B2B (DC-DC Charger). The MPPT will be in the highest voltage for a certain time before it drops down to float mode so the situation isn't constant.

You could maybe lower the Absorption Voltage a little on the MPPT make it more acceptable to the Starter (I have gone for this option on a new Multiplus setup for a campervan where a Cyrix is also in play and will connect a wet cell Starter and AGM Leisure/House Battery).

You could add a switch to the earth connection to the Cyrix so you can manually disconnect it when you think the Starter has 'had enough'.

Or you could change the Starter Battery for an AGM Battery? I took this approach with my own van where I had 4 x 110AH AGM Batteries for a Leisure Bank and fitted a 5th one (same brand and model) as a Starter Battery so the requirements were identical (not withstanding temperature variances, but can only go so far ;) )


The B2B Approach is probably the best though :)

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David avatar image
David answered ·

With the reference to Renogy, I am going to assume you are in the US? A good B2B Charger Range are the Australian Redarc range. Excellent kit but can be a little pricey. A good option and one I recommend to people in the UK is the Ablemail B2B - available as 20A, 30A and 60A and are rock-solid. Designed AND actually MADE in the UK by Ablemail (the company) and with a 2 year warranty. I don't think they are distributed in the US, but may well be in Europe though?

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dannen avatar image dannen commented ·

Thanks for the answers!

I'm from Sweden so i'll try to find a OK priced B2B charger in the EU.

Seems like B2B charger is the best and easiest option(other than going for a AGM startbattery, but i think the price is roughly the same as a B2B charger)

I cant seem to find a Victron B2B charger other than the Buck-Boost but the price is to high for me i'm afraid.

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Fra avatar image
Fra answered · 
I have the same configuration as you: agm service batteries 90 + 100 in parallel and acid flooded Starter battery.

I have a 300 watt panel and a Tracer 3210 an regulator set with an absorption voltage of 14.4v and an average absorption time of 120 minutes.
This configuration is fine for agm and flooded start battery.
You won't have any problems.
They are always lead-acid batteries and not gel.
They should be safely loaded together.

As they suggested, you can put a switch on the negative of the cyrix to exclude it when you don't need it.
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