On board DC to DC charging Lithiums

[fishtragic]

Hi all,
Are any of you using the Sterling Pro B 12v to 36v for on board charging Lithium batteries. Wondering if it will take the possible 70A from the outboard alternator and if it will deliver enough charge on spot to spot moves to make it worth while?

[NAGG]

I can’t answer your question on the sterling pro ….. and I certainly want to look into DCDC charging for my lithium leccy batteries as well . Can it handle 2 x 12 volt batteries ?. What is the charge rate ?
As for the effectiveness of this set up …. It really boils down to how much running around you do …. How long are your runs because unless you can put enough charge into your batteries it’s not that beneficial. … other than something is better than nothing. We looked into these things back in the days of fishing impoundments…… the runs were just too short & we never ran our motors long enough
If you do big trips or are off grid …. Awesome. That’s where it would be great …… head out to the reef for the day and on the hour or two run home you may have replaced what you have used .
Really interested in what you come up with

Chris

[disorderly]

. It really boils down to how much running around you do …. the runs were just too short & we never ran our motors long enough
If you do big trips or are off grid …. Awesome. That’s where it would be great …… head out to the reef for the day and on the hour or two run home you may have replaced what you have used .


Chris

What Chris said are exactly the key points..

Assuming your batteries are fully charged when leaving for your fishing spot then the only charge going into the batteries is when you are moving spot to spot..

So then assume that the alternator will put back 50 useable amps into your batteries per hour and divide that by 3 ..

So for a 36 volt system you may have to run the motor for an hour to put back in 15amps.

Even the trip home will only partially top them up depending on the distance..

I crunched all the numbers and for my reef fishing trips I couldnt see the benefit of a dc/dc charger..

I also looked into solar panels but found that the batteries couldnt be charged while the motor was being used but this might still be an option in conjunction with a gennie and charger for longer camping trips...

You would have to used a solar panel rated for 45v plus or have 2 in series..

I'm not sure how much you have used the system but 36v will carry 50% more energy then a 24v in comparison and I have found it very surprising how long I get out of my 100 Ah lithiums....but I dont generally bottom fish in anything over 15 knots because the propeller starts bobbing out of the water....I have never taken my batteries anywhere near empty in 2 years and we do plenty of overnighters..

By far the easiest is to just buy bigger batteries initially and charge them with a 240v charger at home...

[stevej]

That’s the conclusion I’ve come too
I’ve made space for more lithium’s have made room for 2 for the trolling motor one for the Sounders and keep a lead acid for starter
saving for the three lithium’s atm

200 amp hours of lithium’s is equal three 100 amp hour lead acids maybe more

[ranmar850]

You can buy DC-DC chargers with a solar MPPT charger built in. So all inputs are taken care of--the ones I use actually prioritise solar input, if it is present, over draw from the alternator, up to your max rating. So you will always be getting max charge rating. Just be aware that not all lithiums are suitable for parallel operation, it depends on the BMS fitted, and the manufacturer generally states whether or not it can be done.

[NAGG]

That’s the conclusion I’ve come too
I’ve made space for more lithium’s have made room for 2 for the trolling motor one for the Sounders and keep a lead acid for starter
saving for the three lithium’s atm

200 amp hours of lithium’s is equal three 100 amp hour lead acids maybe more

Theoretically you have 150 amps with 3 x 100amp lead acid (50% DOD) vs 180-190amps for Lithium .

I'm waiting for my Lithium starting battery to arrive today ...... something like 6kgs

Chris

[NAGG]

What Chris said are exactly the key points..

Assuming your batteries are fully charged when leaving for your fishing spot then the only charge going into the batteries is when you are moving spot to spot..

So then assume that the alternator will put back 50 useable amps into your batteries per hour and divide that by 3 ..

So for a 36 volt system you may have to run the motor for an hour to put back in 15amps.

Even the trip home will only partially top them up depending on the distance..

I crunched all the numbers and for my reef fishing trips I couldnt see the benefit of a dc/dc charger..

I also looked into solar panels but found that the batteries couldnt be charged while the motor was being used but this might still be an option in conjunction with a gennie and charger for longer camping trips...

You would have to used a solar panel rated for 45v plus or have 2 in series..

I'm not sure how much you have used the system but 36v will carry 50% more energy then a 24v in comparison and I have found it very surprising how long I get out of my 100 Ah lithiums....but I dont generally bottom fish in anything over 15 knots because the propeller starts bobbing out of the water....I have never taken my batteries anywhere near empty in 2 years and we do plenty of overnighters..

By far the easiest is to just buy bigger batteries initially and charge them with a 240v charger at home...

All of these DCDC chargers I've looked at seem to only have around 10-20amp input for a 2 or 3 battery array .
For me a full days spot locking could see 50-80 amps pulled & you certainly wont replace that using DCDC charging. ..... so unless I can pump in 30-40 amps / hr into each battery I'm resigned to needing to take my Honda genny with me ..... that combined with two 25amp Victrons will see the batteries up to float (95%) in 2-3 hours.

Chris

[Lovey80]

You can buy DC-DC chargers with a solar MPPT charger built in. So all inputs are taken care of--the ones I use actually prioritise solar input, if it is present, over draw from the alternator, up to your max rating. So you will always be getting max charge rating. Just be aware that not all lithiums are suitable for parallel operation, it depends on the BMS fitted, and the manufacturer generally states whether or not it can be done.

I think Fishtragic is specifically looking for a DC to DC charger that will charge from 12v starter and alternator to a 36v bank. The Sterling Pro is from what I have read, is built specifically to do this. But it seems to be limited to 25A input.

Screen Shot 2021-08-11 at 12.12.52 pm.jpg

Another option is the Yandina Trollbridge. https://yandina.com/troll36info.htm

[Lovey80]

Hi all,
Are any of you using the Sterling Pro B 12v to 36v for on board charging Lithium batteries. Wondering if it will take the possible 70A from the outboard alternator and if it will deliver enough charge on spot to spot moves to make it worth while?

What engine are you running?

[stevej]

Theoretically you have 150 amps with 3 x 100amp lead acid (50% DOD) vs 180-190amps for Lithium .

I'm waiting for my Lithium starting battery to arrive today ...... something like 6kgs

Chris

and 32kg for two lithium’s v 90 for 3 lead acids
jusy keep holding off hoping for a price reduction

[NAGG]

I think Fishtragic is specifically looking for a DC to DC charger that will charge from 12v starter and alternator to a 36v bank. The Sterling Pro is from what I have read, is built specifically to do this. But it seems to be limited to 25A input.

Screen Shot 2021-08-11 at 12.12.52 pm.jpg

Another option is the Yandina Trollbridge. https://yandina.com/troll36info.htm

From memory I dont think the trollbridge does Lithium

Chris

[NAGG]

and 32kg for two lithium’s v 90 for 3 lead acids
jusy keep holding off hoping for a price reduction

You'd be looking at even less weight than that - more like 26-28kgs ...... it's freaky stuff .

My Lithiumax cranker & deep cycle arrived today ..... I chucked them on the digital scale & got 13.6kg combined

Chris

[Lovey80]

From memory I dont think the trollbridge does Lithium

Chris

They apparently have two different types. One specific for lithium

[NAGG]

They apparently have two different types. One specific for lithium

I see that now I know when I looked into it a couple of years back they didn't

So do you know how much charge would go into 2 x 125 amp LiFePO$ batteries via a trollbridge (assume a 40amp alternator) ?

Chris

[ranmar850]

Regardless of brand or type of DC-DC, they can't make power out of nothing. So the most you could expect would be the max output of your alternator, at best. People have been referring to "amps" per day--to keep it straight, refer to them as amp/hours or ah--the number of amp hours you use is what you need to replace. ie, you pull 5 amps for 2 hours, that is 10 amp/hours of capacity used. So you need to put 10 amp hours back in--10 amps for 1 hour, or 20 amps for half an hour. It really is a 1 for 1 equation with LiFePo4 charging, whereas old chemistry requires you to put more back in than you put out.