Battery question

[blazian]

I am currently using a Super Start Marine Battery to run my trolling motor
but I am looking for another battery that is not as heavy, it weighs 57lbs.
So fo the electronics guys out there, what is the equivalent LiPo battery? Is there an equivalent "Reserve Capacity (min)?
My battery specs are:
Group Size (BCI): 27
Cold Cranking Amps (CCA): 840 CCA
Marine Cranking Amps (MCA): 1050 MCA
Group Size (BCI): 27
Reserve Capacity (min): 182 Minute
Voltage (V): 12 Volt

thanks for any help

[Mr_Fixit]

Well, LIPOs are measured in mAH.. Miliamps per hour. Superficially, you would look for a lipo that has the equivalent mAH rating. However the problem is far more complicated than that. There are several factors involved with lipos that need to be identified and considered:
1) Discharge Rate - Lipo discharge rate is defined/limited by the number of parallel cells make up the battery. This is often measured in a C rating:

"Example - For a 2000 mAh battery with a 15C rating, the continuous current that may be drawn out of the battery is 2000 mAh x 15 = 30000 mA, or 30 Amps (A) (divide by 1000). There is also another rating that is applicable to a battery known as peak or "burst" current discharge rating."

2) Discharging a Lipo can be damaging, and in some cases dangerous. Unlike LiIon and most other battery types, you can not drain a lipo entirely. Doing so permanently damages it. Because of this, all systems designed to be used with a Lipo are built with a buffer of about 20%. Also, there is an upper max charge of about 10%. So realistically, the useful capacity of a lipo is only about 70% of the total design capacity. Overcharging and draining can both damage them. This damage would result in reduced functionality of the battery and could in some cases result in a very nasty fire.

3) As mentioned in 2, charging a battery has to be handled carefully. Special charging systems should be used. Never use a non-lipo charging system. This is even more important for multi-cell lipo setups. Each cell must be balanced, otherwise you run the risk of one or more cells being damaged due to over/under charging (See #2)

4) Now with most of the caution provided, there are some fairly serious benefits from using LIPO: The energy to mass ratio is rather insane. I dont remember the ratio, but your 57lb standard battery would only weigh a fraction of that in Lipo. In RC Airfraft, this is about a 40-50% weight savings, and you often get a bit more power.

I know this did not answer your core question, but hopefully the information provided can help you better understand the scope and concerns you are stepping into here. Once you identify your battery (Lipo), you will need to install a control system between the battery and your motor to ensure the battery does not discharge beyond 20%. You will also need a charging setup for your LIPO, which will most likely be 4+ cells.

Originally Posted by blazian

I am currently using a Super Start Marine Battery to run my trolling motor
but I am looking for another battery that is not as heavy, it weighs 57lbs.
So fo the electronics guys out there, what is the equivalent LiPo battery? Is there an equivalent "Reserve Capacity (min)?
My battery specs are:
Group Size (BCI): 27
Cold Cranking Amps (CCA): 840 CCA
Marine Cranking Amps (MCA): 1050 MCA
Group Size (BCI): 27
Reserve Capacity (min): 182 Minute
Voltage (V): 12 Volt

thanks for any help

[Harry Hill]

Lipo batteries are about 4 volts per cell, so they are run in series to get your voltage, 3 in series, express as 3S would give you about 12 volts, then they are run parallel to increase the amps. Normally the higher the C rating the more expensive the battery is. You can run them in parallel as far as you like to increase amps. The higher the C rating the more usable power you have. As said in the previous post you need a dedicated charger for LiPo or you will blow the battery up. A LiPo fire is white hot and cannot be easily extinguished, it will burn a hole right through your kayak. Currently I run a 3S 4500mah 30C battery for my fish finder and run about 6 hours without getting it dangerously low. You cannot take the individual cells below 3 volts or it will ruin them, after 6 hours my battery is at 10.8 volts. Lithium Ion expressed as LiIon is safer to use but doesn't give you quite as much as usable power. Check Hobby King USA to get an idea about batteries and prices. How many amps does your motor pull?

[alanw]

Good info here. That battery is probably around 70AH (check their website). Looks like you need more AH from a lipo than for a lead battery to get the same usable power? That's gonna be costly, I saw a 70 AH lipo for $1200.00

[Harry Hill]

you really need to know how many amps your motor pulls, just a 10 amp LiPo battery is about $200

[blazian]

I have a Minn Kota 40, so drawing 40 amps about. Might be too expensive to go with LiPo