That certainly is a good price for that battery and accoutrements.
There are a few things one should know regarding these.
They have an ~18 AH AGM battery in them.
These batteries are not immune to all the other things which kill other lead acid batteries, nor are they immune from the charging requirements of other AGM lead acid batteries.
These AGMS do not have the super low self discharge of higher quality AGMs, and like all AGMS, can be tickled to death when cycled deeply and then fed very low current for a very long time.
The charger which comes wth these booster packs is a single voltage, low amperage charger. Likely capable of 0.5 to 0.75 amps maximum, and it will put that out until ~13.6 to 13.8v is reached, and then hold that voltage as long as it is plugged in. The green light which comes on indicating full charge is not to be trusted as the ONLY way to know when an AGM is fully charged, is when amperage at ABSORPTION voltage tapers to 0.5% of the battery capacity. Full charge cannot be determined by amperage at float voltage. It can be guestimated only and that guess will likely only be 80% accurate and only relevant for a short period of the battery's lifespan when it is newer.
When the battery is new, these low currents for long enough can fully charge the battery, but once aged, 13.8v forever will never actually fully charge the battery, especialy not when the maximum current is only 0.5 amps and the battery could no longer charge a cell phone( 5 to 10 watts).
An 18AH AGM discharged below 50% would
ideally want 5 to 6 amps until it is brought upto 14.5 to 14.9v, and held there until amperage tapers to 0.09 amps or so. At that point the included charger can hold it at 13.6 to 13.8v float voltage and prevent self discharge, but the included charger cannot even come close to what this battery would ideally want for maximum longevity and performance during that lifespan.
But there is no doubt these jumper packs are convenient and can easily help a depleted starting battery to turn the engine over, but they likely cannot, by themselves, turn over any but the smallest engines in warm temperatures and likely only then, when the battery is still new and healthy and at or near maximum capacity.
If used as a house battery and drawn down deep, and only recharged wth the included charger, the battery within them wll NOT last very long and might not have the gusto to do its job of jumpstarting the engine when required. Could be a false confidence. So I recommend people save them solely for jumpstarting and use their larger engine battery for USB and 12v ciggy stuff.
The battery within is not all that difficult to replace. They range from about 38$.
https://www.amazon.com/Mighty-Max-Batter...ting-goods&ie=UTF8&qid=1539475827&sr=1-5&keywords=18+Ah+Agm
This is the type pf product which goes on sale when the batteries within are likely sulfated, as these batteries will self discharge 5 to 9% per month or so, and once under 80% charged and left there to still discharge, the sulfates are unlikely to ever redissolve backinto the electrolyte, and certainly will not do so with the included charger at 13.8v and half an amp to achieve that.
I have no recommendations for a proper charger for these 18Ah AGMs when regularly deeply cycled, but ideally, one should seek 5 to 6 amps and an absorption voltage of 14.5 to 14.9v, and be able to hold that voltage until amperage tapers to very low numbers.
These Chinese AGM batteries, if they get the proper recharge regimen and do not sit for very long in a discharged state, are actually surpisingly durable. But they can be heavily sulfated new off the shelf, depending on how long they have been sitting and self discharging.
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